A mobile network is a network whose hosts and routers are usually static (e.g., non-mobile) with respect to each other, but are collectively mobile with respect to the rest of the Internet. For example, a mobile network might be found in an airplane, a ship, or a train. In general, a mobile router provides mobility (e.g., connection to the Internet Protocol (IP) infrastructure) for the nodes attached to the mobile router using, for example, mobile IP or network mobility (NEMO) protocols. A specific node in the mobile network is typically designated the mobile router and manages the mobility for all of the nodes within the mobile network, and thus a mobile network can change the point of attachment to the IP infrastructure while maintaining IP communication between nodes inside the mobile network and corresponding nodes connected to the Internet. When the mobile router moves from one IP subnet to another, the mobile router is typically required to handle mobility so as to maintain all of the communication of the nodes attached to the mobile router.
Mobile networks may take a variety of configurations such as a nested mobile network configuration where at least one first mobile network is attached under a second mobile network. For example, the first mobile network may be an individual carrying a device having an associated personal network, and the second mobile network may be a train having a mobile network infrastructure with connectivity to an IP network or infrastructure. When the individual enters the train, the mobile network of the individual can communicatively couple to an access point deployed in the train to operate within the mobile network of the train. Each mobile network has one or more local fixed nodes (LFNs) (e.g., a wireless device) that may be connected to the mobile router of the corresponding mobile network, such as by Ethernet or 802.11. The LFN has an IP address that belongs to the IP subnet(s) of the mobile network and has no specific IP mobility support. Each mobile network can also have one or more home mobile nodes (HMNs) that may be connected to the mobile router of the corresponding mobile network. An HMN is referred to herein as a mobile node (typically running Mobile IP protocol) having a home network that is the mobile network to which the HMN is attached. The HMN has a home address that belongs to the IP subnet(s) of the mobile network and has the same home agent (HA) as the HA of the mobile router of the corresponding home mobile network (i.e., the home agent of the HMN is not in the home mobile network of the HMN). Each mobile network can also have one or more visiting mobile nodes (VMNs) that may be connected to the mobile router of the corresponding mobile network. A VMN is referred to herein as a mobile node (typically running Mobile IP) attached to a mobile network that is not in the home network of the VMN. The VMN has a home address, and configures a temporary address, or care-of address, that belongs to the IP subnet(s) of the mobile network to which the VMN is attached. A Vehicular Area Network (VAN) having a mobile network deployed in a vehicle is an example of a mobile network in practice.
Prior to establishing IP communication with a destination node, the destination hostname is resolved into the IP address associated with the destination node, referred to as “name resolution”, unless the IP address is previously known. One or more domain name system (DNS) servers may be used for a successful name resolution and typically involves a set of intermediate DNS servers having connectivity with one another to enable name resolution. For example, a mobile router has connectivity with a first DNS server, and the first DNS server has connectivity with a second DNS server that is authoritative for the destination node.
This name resolution is then used to establish IP communication. Mobile IP or NEMO protocols support routing between a node in one mobile network of a group of mobile networks with a node in another mobile network of the group of mobile networks using home agents to establish communication between the two nodes. A home agent is referred to herein as a node in the IP infrastructure that intercepts communication addressed to a particular LFN and re-directs the communication to the current location of the mobile router associated with the LFN.
Mobile nodes in an IP network are supported using a mobile IP protocol which allows a mobile node to change from one IP subnet to another while maintaining on-going communication. The mobile node has a permanent address, or a home address, that is used for communication. Each time the mobile node attaches to a new access point, a new temporary address, or care-of address, is assigned to the mobile node. The mobile node sends a binding between the home address and the care-of address to a server in the network, or a home agent. When a node in the Internet attempts to send a packet to the home address of a target mobile node, the packet is routed to the home network of the mobile node where the home agent intercepts the packet. The home agent, using the binding received from the mobile node, tunnels the packet to the care-of address of the mobile node so as to re-direct the packet to the current location of the mobile node. For example, standard node mobility protocols (e.g., mobile IP) and network mobility protocol (e.g., NEMO) utilize a bi-directional tunnel between the home agent and the mobile entity to maintain on-going communications as the mobile entity changes points of attachment to the IP infrastructure. This routing is complex, particularly for communications between a fixed node (e.g., a local fixed node (LFN)) in the mobile network and a visiting mobile node or between two visiting mobile nodes attached to the mobile network.
When establishing communication between an LFN and a visiting mobile node in a mobile network, the LFN sends the communication packet to the home address of the visiting mobile node. For example, the LFN sends the packet to a default router (e.g., a mobile router (MR1)), and the default router applies the mobile IP mechanism and tunnels the packet to a home agent (e.g., a mobile router home agent) in the mobile router home link. The mobile router home agent de-encapsulates the packet and sends the packet via the Internet to the home link of the visiting mobile node associated with the home address. At the home link of the visiting mobile node, the home agent of the visiting mobile node intercepts the packet when the visiting mobile node is not attached to the home link and tunnels the packet (first encapsulation) to the care-of address of the visiting mobile node. This care-of address of the visiting mobile node belongs to the mobile network. The tunneled packet from the home agent of the visiting mobile node is routed to the home link of the mobile router. The home agent of the mobile router intercepts the packet and tunnels the packet (second encapsulation) to the current location of the mobile router. The mobile router de-encapsulates the packet (e.g., removes the second encapsulation from the home agent of the mobile router) and sends the packet to the visiting mobile node. The visiting mobile node removes the remaining first encapsulation from its home agent and retrieves the initial packet sent by the LFN. This routing through the home agents located in the IP infrastructure places overhead on the radio interface between the mobile router and the IP infrastructure because packets to be routed between the visiting mobile node and the local fixed node will be sent twice over this interface (e.g., in the upstream and downstream directions). Additionally, overhead is introduced on the radio interface between the mobile router and the IP infrastructure because of the encapsulations used for routing the packets (e.g., bandwidth consumption).
In a conventional mobile network, while the mobile router having connectivity to the IP infrastructure maintains this connectivity, communication may be established between nodes of the mobile network (e.g., LFNs and VMNs) using conventional mobile IP. When the mobile router loses this connectivity, the mobile network is isolated and referred to as “autonomous”. When the mobile network is in an autonomous mode, the mobile network is disconnected from the IP infrastructure and the corresponding home agent, and the home agents (e.g., of VMNs) are not reachable by the mobile router. Currently, conventional protocols, such as Mobile IP and NEMO, do not support the transmission of data packets (i.e., routing) between two nodes in an autonomous mode. In addition, the node initiating the communication may generally know the fully qualified domain name (FQDN) of the destination node but may not know the IP address of the destination node. With the loss of connectivity to the IP infrastructure, the nodes of the mobile networks (e.g., LFNs) lose access to DNS servers (e.g., default DNS servers, authoritative DNS servers, and intermediate DNS servers) that would otherwise be used for name resolution of the FQDN of the destination node (e.g., VMNs) into the IP address of the destination node.